1. Field of Invention
The present invention relates to building systems and, more particularly, to a building system incorporating rolled metal mullions accommodating the mounting of glass panels and the like.
2. History of the Prior Art
The prior art is replete with building systems incorporating a wide variety of structural mullions and panel mounting systems. These mullions are, in many instances, fabricated from extruded aluminum which provides the necessary structural support and the often complex cross-sectional configuration needed for a particular application. The shape varies between applications because a variety of designs are needed for structural and functional considerations relative to mounting numerous types of panels, such as glass, therebetween. Many conventional mullion assemblies are made from aluminum due to the fact that aluminum is both strong and may be economically extruded into the complex shapes necessary for facilitating glazing of glass panels thereon.
There are many significant parameters in the design of a building system utilizing glass panels and the like. Considerations of structural strength and glazing are two major parameters. Structural strength can be provided by very basic shapes including simple rectangular tubular designs. The necessity of incorporating pockets for receiving and sealing the edge of the glass does, however, present itself as a fabrication complexity. The complexity of the cross-sectional shape for the region of the glazing pocket has prevented widespread utilization of any material other than aluminum in today's building industry. In fact, roll-formed steel has been used in the past for not only storefront designs but also curtain wall constructions. These members are usually rolled into a cylindrical or box shape and welded. In these designs, however, the problem of mounting and sealing glass panels between mullions has substantially eliminated widespread commercial use of simple roll-formed steel. For example, conventional rolled steel columns of the type typically used in storefront areas are generally incapable of affording flush-glaze mounting of glass. To date, aluminum has been the most widely accepted mullion material for curtain wall and many storefront assemblies.
It may be seen that a significant advance within the prior art would be to provide a structural building system having the advantages of extrusion molding and roll-forming in a single system. In this manner roll-formed structural metal such as steel could be interconnected with glazing and mounting elements having a more complex cross-sectional configuration. Many prior art designs utilizing two or more materials in a single assembly are seen in several U.S. patents. These developments have addressed numerous aspects of panel designs and functional considerations for partition structures, window assemblies, column coverings, framing techniques and the like.
U.S. Pat. No. 3,371,454 issued to R. N. Anderson is a 1968 patent for a partition structure. In this patent a partition assembly is constructed with posts and horizontal members formed from aluminum extrusions. A generally H-shaped core part is formed with corner regions defining four intermediate recesses therebetween. Panels are constructed of material such as sheetrock or glass and secured between the posts and horizontal members by means of glazing channels. The glazing channel is constructed therein of polyvinyl chloride or similar semi-rigid resilient plastic and is constructed to be used in any of the four recesses of a post or a horizontal member to which it is desired to secure a panel. Closure strips are also shown to be formed of polyvinyl chloride and may be utilized to enclose any recessed area not used for a glazing channel. This combination of plastic and aluminum teaches an integration of different materials for a partition structure capable of non-destructive erection.
U.S. Pat. No. 3,225,502 issued to W. Hallauer is a 1965 patent for a composite frame. A frame of solid wood, metal or synthetic resin is taught in combination with steel clips on order of 0.5 millimeters thick. The clips engage recesses formed in the frame and in a cover strip which overlaps some longitudinal sides of the frame. The visible surfaces of the cover strips are relatively flat and in an assembled configuration define a glazing cavity therewithin. In this embodiment the structural member is enclosed within the covered strips and the structural element enclosed therein.
U.S. Pat. No. 4,648,231 issued to Francois X. LaRoche is a 1987 patent which teaches a structural joint element for panels. A primary structural joint is therein provided for panels such as glass joined together at the edges to a supporting structure such as a column. A relatively thick walled structural member, or beam, is thus constructed with a plurality of recesses for receiving a molded part in the form of a joint element therein. The joint element is utilized in combination with a molded cover strip in the mounting of glass panels to the structural beam. The joint element is constructed of substantially thinner wall construction in that it is provided in a mounting configuration for the cover strip.
U.S. Pat. No. 3,975,881 issued to James Ninowski, Jr. is a 1976 patent teaching a window frame assembly. Both aluminum and vinyl are incorporated into a frame assembly comprising an exterior frame member, an interior frame member and cooperating locking means such as snapping connections intricately formed with each of the members. The vinyl provides improved thermal qualities incorporated into this configuration. The extruded structural aluminum is specifically adapted to the particular application for the vinyl extrusion.
The above described prior art of multi-material framing/ construction manifests the direction of the prior art in attempting to utilize the most economical and useful material in a particular application. The particular application in the present invention includes relatively low-loading, storefront type mullion construction as well as some curtain wall systems. In such a construction a structured wall assembly is provided with glass panels disposed between the various horizontal and vertical structural elements. One example of such an assembly is shown in U.S. Pat. No. 3,352,078 issued to H. B. Neal. This 1967 patent utilizes a two-piece frame assembly, both formed of aluminum, to mount glass panels therebetween. The frame members are aluminum extrusions and have a generally uniform cross-section throughout their entire length. It is well known to utilize expansion joints in such constructions and this aluminum extrusion approach has thus found widespread popularity in the prior art. Most conventional mullion assemblies in such storefront profiles are made from aluminum due to the fact that the mullion shape is somewhat complex, not lending itself to roll-forming, and aluminum may be extruded. Strength is necessary for the assembly and some degree of complexity in the cross-sectional configuration is necessary for interconnection and glazing assemblies. These are seen in the Neal Patent. Other construction techniques using configurations as simple as box-shaped and cylindrical steel columns have, of course, found utility. Early attempts for curtain wall construction even incorporated roll-formed steel. One problem was the tooling necessary for particular jobs, as well as limitations in the shape that could be roll-formed. Tooling for roll-forming steel is considerably more expensive than for aluminum extrusion. For this reason, as well as shape limitations, the use of roll-formed steel has not found itself applicable to many conventional designs utilizing glazing strips. One exception is that provided by Carmel Steel Products of Santa Fe Springs, Calif. wherein steel mullions are formed from rolled steel sections. Cornerposts, jambs, vertical and horizontal mullions are therein assembled with flush glaze capacity. A sufficiently heavy gauge steel is apparently used in a welded assembly to carry the requisite static and dynamic loads. At one time such heavy gauge steel was too expensive for many applications. Changes in the relative prices of aluminum and steel have, however, necessitated a closer look at this issue.
The true, underlying needs in the design and fabrication of building system storefront mullions include considerations of strength and flexibility. Sufficient structural strength is necessary for withstanding the static and dynamic loads and design flexibility is needed relative to the glazing pocket and the glazing insert. Moreover, very thin walled steel would provide less weight and cost if a structural system could be implemented therewith that could meet the loading parameters. It would thus be an advantage to overcome the problems of the prior art by providing a system that incorporates the structural and cost advantages of thin walled, roll-formed steel as well as that of extruded aluminum. The present invention provides such an assembly by utilizing thin gauge, roll-formed steel as a comprehensive structural member and, with the glazing pocket necessitating very little structural rigidity, a lightweight material such as plastic may be molded or extruded into the requisite shape. In this manner the simplicity of various roll-formed steel designs and the lightweight, thin-walled, cross-sectional configurations thereof which provide much greater structural strength than material such as aluminum may be incorporated with such materials as plastic or aluminum to provide all the advantages, including appearance, of an extruded part with less cost, a thinner wall construction and greater reliability. In addition, the present invention provides a building system incorporating roll-formed metal that does not require welding or the wall thickness generally considered necessary in prior art systems.